This invention relates generally to improvements in prosthetic devices used for reconstructing human joints, such as a knee joint, hip joint, etc. More particularly, this invention relates to an improved prosthetic component and related method for cemented attachment of the prosthetic component to a prepared patient bone, in a manner achieving a substantially optimum strength attachment interface.
Artificial or prosthetic joint mechanisms for implantation into animals, particularly humans, have been the subject of intensive research and development efforts for many years. Such prosthetic joint mechanisms have typically comprised one or more implant components formed from a relatively biostable material having selected structural properties and a unique shape to replace all or part of a selected anatomical joint, for example, a hip or knee joint. The implant components are installed by surgically accessing the joint and by resection of one or more bone surfaces to accommodate direct attachment thereto of the implant components. One common attachment method has utilized bone cement, such as a methyl methacrylate-based cement or the like used as grouting material to fill up the space between the resected bone surface and the prosthetic component. Alternative attachment methods have relied upon surface coatings of controlled porosity on the prosthetic component in a position to achieve post-operative bone and/or tissue ingrowth.
Although cemented attachment of the prosthetic component can be performed relatively quickly and easily, and does not require a post-operative period during which the strength of the attachment interface is increased (e.g., by bone ingrowth), certain problems and disadvantages exist with respect to cemented components. More specifically, in a typical procedure, bone cement is applied to an attachment surface formed on the prosthetic component, and this attachment surface is then pressed against the prepared patient bone to achieve cemented fixation. However, during such press-on placement, some of the bone cement is normally extruded laterally outwardly from the attachment interface and is lost. Moreover, the prosthetic component can be pressed onto the patient's bone in a slightly cocked or tilted position, so that the thickness of the cement mantle is thicker in some areas and thinner in others. Such nonuniform cement mantle thickness can result in an attachment interface having less than optimum strength, thereby creating an undesired risk of post-operative separation of the prosthetic component from the patient bone.
There exists, therefore, a need for further improvements in prosthetic components of the type adapted for cemented attachment to a prepared patient bone, to provide a cement layer and mantle of controlled and substantially uniform thickness at the attachment interface. The present invention fulfills these needs and provides further related advantages.